Automatic test equipment provides the ability for semiconductor device manufacturers to test semiconductor devices. By testing every device, the manufacturer can reject or accept the device and separate those rejected prior to them entering commerce.
Testing a semiconductor device typically involves the application of known signals to specific pins while measuring the output reaction of the device to those input signals. The output signals are then compared to the expected reactions and to determine whether the device under test (DUT) matches specified parametric limits.
Analog/mixed signal automatic test equipment architectures have traditionally been designed with sets of instrumentation organized by function with higher cost instruments provided as shared resources and lower cost functions provided as pin by pin resources. For example, low accuracy DC sources and meters provide a quick and inexpensive shorts/open test at every pin while a shared high accuracy DC source and meter might provide the accuracies necessary for parametric evaluation. All Analog/mixed signal automatic test equipment architectures contain a computer with test software to execute the tests automatically in sequence.
Analog/mixed signal automatic test equipment software architecture traditionally follows the linear flow programming models, where a single test program runs a single device under test in a very specific sequence. The program ends when the tests are gathered and evaluated against pre-programmed test limits and a pass/fail determination is made.
A variation on the linear flow programming model has been in use under the name of multi-site testing in which a single test program running multiple identical DUTs synchronously is performed.
In both types of analog/mixed signal automatic test equipment software architecture, the job program testing the device under test is given full control of all of the resources within the tester. This means that all resources not needed to test the particular device under test remain idle for the duration of the test program. Importantly, traditional analog/mixed signal automatic test equipment software architectures do not allow the use of the unused resources for any other tasks during testing.
Traditional automatic test equipment software architectures may use unique and proprietary languages and/or language structures. They also generally contain unique and proprietary bus structures. Users write job programs for this automatic test equipment and commonly the cost of writing these job programs exceeds the capital cost of the automatic test equipment. In order to change to another brand of automatic test equipment or to a newer version of the current system, it is frequently necessary to port these programs to a new proprietary language at great expense.
Typical automatic test systems have a single executable job program running within a computer's operating system. This means that the control of the program is generally local to the computer that is running the tester. They do not allow for the running of the tester remotely. Since many of these testers operate within clean room environments, it is necessary to go to the tester for debugging or setup of the program. Large losses of productivity can sometimes be traced to the suiting up process prior to entering a clean room environment.
Typical automatic test system architectures have a single job program written and run in the regional language (English, Japanese, French, etc.) of the test system developer. This means that the user of the tester may have to understand the language of the tester manufacturer in order to adequately communicate tester performance during maintenance assistance from the tester manufacturer. Since tester performance is frequently an interpretation of test results from specialized job programs, communication can be difficult across language barriers.
There are several prior art test systems such as the Teradyne A360 analog test system. The A360 system is an automatic test equipment (ATE) that has a physical instrument called “M601.” The M601 instrument contains seven V/I sources, one voltmeter and a 9 line×48 pin cross-point matrix. The cross-point matrix connects any one of the V/I sources or the voltmeter to any one of the 48 DUT points (as described in “A360 Test Engineer's Manual” published by and available from Teradyne Inc., 321 Harrison Ave, Boston, Mass., 1984). For example, in the A360 tester job program, a user can connect 10 volts to DUT pin 1, and 0 volts to DUT pin 2, and the Voltmeter to DUT pin 3. In such a case, the A360 test program sets one of the M601 test instrument's seven V/I sources (e.g., S1) to 10 v, connects this V/I source to one of the cross-point matrix lines (e.g., Line 1) and then closes the cross-point relay between line 1 and DUT pin 1. Similarly, the A360 test program sets S2 to 0 volts and connects it to, e.g., Line 2 and closes the cross-point relay between line 2 and DUT pin 2. The A360 test program can also connect the voltmeter to Line 9 and close the cross-point relay between Line 9 and DUT pin 3. There are several disadvantages with this architecture that allocates resources to the test job programs at the initialization time and releases them only at the end of the program.
The A360 also has a physical instrument called “M625.” The M625 instrument is an AC source and measurement instrument consisting of two AC waveform generators for sourcing and a set of notch filters for input, and an AC to DC converter. The output of the AC-to-DC converter can be connected to a system DC voltmeter for measurement of AC waveforms. The instrument can also be directly connected to the DUT (as described in “A360 Test Engineer's Manual). In a tester job program, for example, the instrument generates a 100 Hz sine wave as a source to the DUT, and then it measures the harmonic noise component of the DUT's output. In this example, the DUT's output is primarily 100 Hz with a noise component. The instrument measures the output using a notch filter at the primary frequency to eliminate the 100 Hz primary frequency component so that just the harmonic noise is detected. The noise passes through a bandpass filter that is set to the harmonic frequency of interest. The AC to DC converter then delivers to the DC voltmeter a DC voltage proportional to the amount of harmonic noise at the output. This process is repeated over and over again with different bandpass filter frequencies to measure the different harmonic frequency contents. This architecture is again relatively inefficient.
The A360 also has a physical instrument called “M602.” The M602 instrument is a single instrument has two high stability limited range voltage sources and one high precision voltmeter. This instrument can be directly connected to a DUT. A tester job program, for example, may need to provide a highly stable voltage of 10.0000 volts to a DUT to measure the DUT's output with very high precision. The instrument sets one of its two high stability sources to 10.0000 V and connects the M602 meter to the DUT's output for measurement. However, this architecture is relatively inflexible since it cannot flexibly replace the connected meter with a meter having a higher accuracy (such as the precision calibration meter of the instrument primarily used for test calibration).
Furthermore, there are several prior art test systems called “virtual test instruments” or “virtual front panels” of test instruments. These test instruments use a windowing software package (for example, Microsoft Windows® or Measurement Studio® by National Instruments) to provide the equivalent of an instrument front panel in a software form. In these virtual instruments, buttons and windows and indicators replicate or mimic the front panel of a benchtop standalone instrument (e.g., a digital multi-meter, DMM, or a current source). The “virtual front panel” of these instruments replaces all or part of the buttons, knobs, and indicators that would normally be on a front panel of a higher-level instrument.
Furthermore, there are virtual instruments (e.g., provided by National Instruments Inc.) that provide a common front panel for multiple different vendor implementations of a common instrument. For example, all DMMs share common attributes such as voltage range setting, a voltage metering indicator, etc. This single common “virtual front panel instrument” is suitable for operating instruments by different vendors or different models. The term “virtual instrument” also describes the use of a common language API (application programming interface) specification for multiple similar instruments, as embodied in the Virtual Instrument Software Architecture (VISA) standard (IEEE 488.1 and IEEE 488.2).
There is still a need for an automatic test system that solves at least some of the above problems or drawbacks.